Flash discharge tube and light-emitting device equipped with the flash discharge tube

A flash discharge tube comprising:

• a light-transmitting envelope;
• a pair of discharge electrodes configured with an anode and a cathode which are respectively hermetically sealed at both ends of the envelope with xenon gas being sealed inside the envelope;
• a trigger circuit for outputting a trigger signal;
• and
• a trigger electrode disposed on an outer surface of the envelope, the trigger signal being applied to the trigger electrode,
• wherein the pair of the discharge electrodes includes tungsten pins disposed inside the envelope, the pins facing each other;
• the envelope includes a central region configured with an alkali-free glass except for quartz glass, the central region serving as an alkali-free region and becoming in a high temperature state during a firing operation of the flash discharge tube, the central region being smaller than a maximum region enclosing a gas-tight space formed by hermetically sealing the pair of the discharge electrodes and being not smaller than a minimum region enclosing an arc-discharge space formed between the tungsten pins of the pair of the discharge electrodes, the alkali-free region containing either no alkali metal component or not larger than a predetermined amount of an alkali metal component;
• and
• the trigger electrode is disposed in the alkali-free region.